Case of overcharging and harassment from FatakPay loan app

I took a loan of only ₹450 from the FatakPay loan app. After that, I have already paid ₹1050 as late fees. Still, these people are demanding ₹6542 from me and repeatedly sending threatening SMS messages, threatening to label me as a Willful Defaulter and to damage my CIBIL score. This is clearly overcharging and harassment. Please mark this number as scam/harassment. Number: [PHONE]